Salaries for parliamentary office staff range from £13,500 to just over £40,000.

Deputy chief whip Tommy McAvoy is among eight members of the
Government's whips office who employ family members, as do at least
five parliamentary private secretaries.

There is no suggestion that any of the MPs have broken any
parliamentary rules on employing family members, many of whom work long
hours during the week and at weekends.

However, the practice was cast into the spotlight by the Derek
Conway scandal after it emerged that he was employing both his sons and
his wife.

Mr Conway was suspended from the Commons and ordered to repay
£13,000 following an inquiry into his "employment" of his son Freddie
as a researcher while he was studying at Newcastle University. He is still employing his wife Colette as office manager.

The fact that so many members of the Government are employing family members has raised fresh questions over the use of public money.

Mark Wallace, of the Taxpayers' Alliance, told the London Evening Standard today: "This is yet another sign that the way Westminster works is outdated and out of touch with the working practices in the rest of the country. We are constantly told that politicians deserve large salaries because they are like executives of large firms. In reality, no private sector executive could turn up and employ spouses or children to work in their office."

MPs, including former Conservative leader Michael Howard, Sir George Young, chairman of the Commons standards and privileges committee, shadow home secretary Chris Grayling, and senior Lib-Dem David Heath, also declare in the Commons Register of Members' Interests that relatives are on their staff.

Alan Keen, Labour MP for Feltham and Heston, employs his son David as constituency manager and senior caseworker. Mr Keen and his wife Ann, a health minister, have faced controversy over the use of public funds to pay for a second home close to Westminster when they have a constituency home nine miles away.

The Government is expected to publish the list of ministerial interests today which may give greater insight into their links to business and any potential conflicts of interests they or their families may have. They could include the financial dealings of ministers' wives and children.

Ministers will have to declare for the first time "relevant interests of spouse, partner or close family members".

Business Secretary Lord Mandelson has sparked controversy by
refusing to reveal his ministerial interests before the official list
is published. His department rejected freedom of information requests
to disclose information in advance.

The new list is
expected to reveal more information about the peer's transitional
funding package after he stepped down as European Trade Commissioner to
join the Government.

The documents could also shed some
light on the financial affairs of supermarket heiress Camilla Sainsbury
as her husband Shaun Woodward is Ulster Secretary.

However, David Cameron could also come under pressure to publish a similar list for the Tory frontbench. Labour has repeatedly sought to exploit the fact that several shadow Cabinet members have a string of directorships which could raise questions of conflicts of interests if they become ministers.

The list of ministerial interests was due to have been published last autumn but was put back following the Cabinet reshuffle.

MPs have been hit with repeated controversies about their use of public funds, particularly the second home allowance. Home Secretary Ms Smith caused a storm after it emerged that she had declared a London home that she shares with her sister as her main residence which enabled her to claim the second home allowance on her constituency home.